If you find reading plans confusing, or have trouble identifying the exact dimensions of wood at a lumberyard or home center, read on. Most lumber is sold in “nominal” (in name only) sizes such as 1x3, 2x4 and 4x4. But these sizes are not the actual dimensions of the wood. The chart below shows the actual dimensions of lumber when it is dry (when wet, it will be slightly larger). This handy chart will help you translate the nominal into the actual (dry). After a while, you'll get the hang of it.
The difference between “nominal” and “actual” dimensions